Gas turbine engines may be used to power various types of vehicles and systems, such as air or land-based vehicles. In typical gas turbine engines, compressed air generated by axial and/or radial compressors is mixed with fuel and burned, and the expanding hot combustion gases are directed along a flowpath and through a turbine nozzle having stationary turbine vanes. The gas flow deflects off of the vanes and impinges upon turbine blades of a turbine rotor. A rotatable turbine disk or wheel, from which the turbine blades extend, spins at high speeds to produce power. Gas turbine engines used in aircraft use the power to draw more air into the engine and to pass high velocity combustion gas out of the gas turbine aft end to produce a forward thrust. Other gas turbine engines may use the power to turn a propeller or an electrical generator.
Typically, the stationary turbine vanes of the turbine nozzle extend between an inner support platform and an outer support platform. The inner and outer support platforms define a portion of the flowpath along which the combustion gases travel. In some cases, to simplify manufacture of the turbine nozzle, the inner and/or outer support platforms along with the vanes are initially formed as segments, and the segments are subsequently assembled together to form a full ring or bonded together. In other cases, the vanes are bi-cast with the inner and outer rings, so that the rings and the vanes form a single, unitary structure.
Although the aforementioned turbine nozzles operate adequately under most circumstances, they may be improved. In particular, requirements for advanced turbine engines calls for increased specific power and reduced specific fuel consumption. These requirements can be met through the use of increased turbine inlet temperatures and increased cycle pressure ratios. However, as the turbine inlet temperature increases, components such as the turbine vanes and blades are exposed to hotter gas temperatures that may exceed the component material capabilities. As such, these turbine components need to be cooled by using air from the exit of the compressor, which bypasses the combustor portion of the engine.
There are various potential of using the compressor exit air to cool the turbine components. First, such operation results in less air being available to cool the combustor, which may reduce combustor durability. Second, another potential effect of air not going through the combustor is higher turbine inlet temperatures, which may lessen the durability of the turbine hardware. Further, because the cooling air is not generating useful work, the result is a higher overall engine specific fuel consumption. To avoid such potential effects, it is desirable to achieve optimum cooling scheme designs in order to minimize cooling flow requirements without compromising the durability of the components.
Accordingly, it is desirable to have an improved turbine nozzle that has improved cooling such that it may operate at higher temperatures without the need for increased cooling flow. It is further desirable to provide such an improved turbine nozzle that is capable of being manufactured using conventional manufacturing techniques. Furthermore, other desirable features and characteristics of the inventive subject matter will become apparent from the subsequent detailed description of the inventive subject matter and the appended claims, taken in conjunction with the accompanying drawings and this background of the inventive subject matter.